Scientists studying soil microbiology have suggested that even a loss of 5 percent of the microbes that inhabit soils could compromise some of their key ecosystem functions.

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The study, published this week, suggests that such a loss could reduce the degradation of toxins in the environment, hampering the microbes' ability to process pollutants.

The complexity and importance of healthy soil is only now being appreciated by scientists and policy organisations. The team behind the paper on Loss of Microbial Diversity in Soils… warned that more research is needed to better understand the functions of healthy soil, and the effects of agrichemicals and waste products.

However, despite the fact that soils – which are formed over many hundreds or even thousands of years – are considered non-renewable by soil scientists, the EU framework for the protection of soils has been stuck at the draft stage for over five years. There are already EU frameworks governing the exploitation of other non-renewable resources such as coal and fresh water, but for now, soil does not have this official status.

Although the NFU in the UK said it does "not believe that there is a need for additional legislation in this area [because] Soils in the UK, and across the EU, are already protected by a range of laws and regulations, " a report released last year by the EU Commission's in-house scientific advisory service, the Joint Research Centre, revealed that soil biodiversity is under threat in 56 percent of EU territory.

The JRC report pointed to "intense land exploitation [which is] estimated as the main pressure on soil biodiversity" and warned that areas of the EU where interest groups have been most successful in their opposition to introducing legal protection for soils (including the UK) also tend to be those where degradation is worst. The latest major UK soil study, conducted in 2009, found that food production is being jeopardised by the loss of two million tonnes of topsoil each year.

The international study published this week was the result of a collaboration between the Universities of Glasgow, Copenhagen, and Oklahoma, SRUC and the James Hutton Institute in Scotland and Swedish Agricultural Sciences University. It was led by Dr Brajesh Singh of the University of Western Sydney.

The group investigated the decline in microbial diversity in agricultural soils. They measured the effects of this decline on soils' ability to deal with polluting toxins. The international team studied the historical build up of pollution from heavy metals like cadmium, zinc, and copper (often from industrial processes) in soils. They said that, in the past, sewage sludge also contained heavy metals which became concentrated in the soil after the sludge was used to improve soil fertility.

Although the concentration of heavy metal used this study was higher than the current EU limit, the work has confirmed that long-term exposure to such contaminants does reduce the diversity of bacteria in the soil.

According to Dr Singh, "If the ability of the ecosystem to remove toxins from the environment is reduced, there will be higher toxicity risks in the environment and for non-target organisms, including humans, from agricultural chemicals. It is likely that these contaminants will remain at higher levels in surface and underground water, as well. It is vital to gain a better understanding of the extent to which soil bacteria are involved in the removal of contaminants."